Mobile or cellular telephones are nowadays perhaps the most common examples of portable electronic communication devices according to the above. Many different digital systems for mobile telecommunications have entered the market in recent years. GSM (Global System for Mobile Communication), for instance, is well-spread across virtually all European countries as well as many places in Asia, Australia, and America. Other common examples are DCS (Digital Communications System), PCS (Personal Communications System), etc. Normally, these mobile telecommunications systems operate in different frequency ranges. In Europe, for instance, GSM uses the 890-960 MHz band, while DCS uses 1710-1880 MHz and PCS uses 1850-1990 MHz. In many countries a plurality of systems are used in parallel to each other, normally operating in different frequency bands, and hence the need for multi-band mobile telephones has become all the more urgent. The need is accentuated by the fact that new kinds of mobile telecommunications services, such as home-based wireless telephones, wireless hands-free sets, wireless LANs (operating in the 2,4-2,5 GHz band), etc, are to be introduced in a near future, or are in fact already here. Consequently, there is an obvious and strong need and demand for communication devices with multi-band antennas.
A general dual or multi-band antenna design is for instance disclosed in WO96/38882 (Ericsson Inc.), where a multi-band printed monopole antenna is operative in two different frequency bands thanks to a parasitic element arranged close to the monopole antenna. The monopole antenna is arranged to be placed, in a conventional way, on top of the telephone apparatus housing. The printed monopole antenna is made from a conductive trace with an electric length, such that a primary resonance occurs within a first frequency band. The parasitic element, which has no direct electric connection with the conductive trace, is arranged to tune the conductive trace into a secondary resonance within a second frequency band.
WO94/25999 (Motorola, Inc.) discloses an antenna, which is arranged in the flip of an electronic apparatus, such as a radio telephone. A transformer is arranged at a hinge mechanism to connect the flip to the main apparatus housing. One transformer winding is located in the apparatus housing, while a second winding is located in the flip. The purpose of the transformer is to couple electro-magnetic energy between the antenna in the flip and other electronics located in the apparatus housing as well as to act as an impedance matching element. The antenna according to WO94/25999 is arranged to work in one single frequency band only.
U.S. Pat. No. 5,337,061 (Shaye Communications Ltd) relates to a wireless telephone with a foldable flip pivotally connected thereto. A first antenna is arranged in the flip, and a second antenna is located in the main portion of the telephone, i.e. the apparatus housing. By carefully selecting the design of the two antennas the need has been eliminated for a separate device for switching between the two antennas. However, the two antennas are arranged to operate in the same frequency band, since the telephone according to U.S. Pat. No. 5,337,061 is aimed at obtaining optimum antenna performance during ongoing calls (wherein the first antenna is operative, and the flip is folded down), as well as in stand-by mode (wherein the second antenna is operative, and the flip is folded up).